For example, the patent document 1 discloses a legged mobile robot, including a trunk unit and two leg links connected to the trunk unit, which walks by alternately advancing the two leg links and landing on the road surface. Generally, a legged mobile robot performs an inverse kinematic calculation based on gait data, which is created on the assumption of a known road surface, and calculates target angles of leg joints such as an ankle joint and a knee joint in order to achieve a trajectory of each section described in the gait data. Note that the gait data is time series data including, for example, a ZMP (Zero Moment Point) trajectory, a center of gravity trajectory, a trajectory of the trunk unit, and a trajectory of foot provided to a tip of the leg link via the ankle joint. Then, the legged mobile robot performs a walking motion by driving leg joints to follow the trajectory of the target angles calculated chronologically. That is, the legged mobile robot is provided with a servo mechanism to make a real angle of the leg joint follow the trajectory of the target angle.
[Patent Document 1]
    Japanese Unexamined Patent Application Publication No. 5-245780